The present invention relates to a method and apparatus for the preparation of powder mixtures by the intermixing/interdispersing to homogeneity of a heterogeneous powder including granulate powders comprising at least 2 different types of powders.
The properties of powders vary depending on their chemical structures. When two or more powders with different properties have been macroscopically and microscopically interdispersed to homogeneity the resulting powder mixture can be expected to have a uniform quality in each lot with respect to such factors as color uniformity. and the aggregation of one type of powder. Thus, such a thorough mixing performance will give continuously stable properties. These highly interdispersed powder mixtures can be effectively used in such fields as cosmetics, pharmaceutical products, resin compositions, paints, inks, art supplies, decorative materials, perfumes, magnetic media, and medical supplies
Methods known for mixing a heterogeneous powder comprising two or more different types of powders include mixing methods based on a stirring effect such as the Henschel mixer, Lodige mixer, and V-mixer, and mixing methods based principally on a shear effect such as a colloid mill, ball mill, motorized orbiting mortar and pestle, and roll mill.
However, these methods are limited in their ability to efficiently and continuously produce microhomogeneously interdispersed powder mixtures from an aggregable powder and a nonaggregable powder. In specific terms, in the case of color-critical applications such as paints, inks, and cosmetics, further improvements in product quality are strongly hindered by the occurrence of variations in color and luster when a powder mixture is used that has particular limitations on its interdispersity at the microscopic level. When an increase in product quality is sought using more vigorous conditions, shear mixing must be carried out for long periods of time, which unavoidably causes a sharp decline in production efficiency. In addition, organic powders become electrostatically charged during long-term mixing, and this causes the problem of re-aggregation.